<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>
	<style type="text/css">
		.a1{
			width: 0px;
			height: 0px;
			border-top: 200px solid transparent;
			border-bottom: 200px solid blue;
			border-left: 200px solid transparent;
			border-right: 200px solid transparent;
		}
		.a2{
			width: 200px;
			height: 200px;
			border: 2px solid black;
		}
	</style>
	<body>
		<div class="a1">
			
		</div>
		<div class="a2"></div>
	</body>
</html>
